The current version of the Internet protocol (IPv4) has proven to be robust easily implementable as well as interoperable and has stood the test of scaling and in the end work to a global utility the size of today's internet. It has not been substantially changed since 1981.
There are several points that the initial design did not anticipate, including the recent exponential growth of the internet and therefore the exhaustion of the IPv4 address space, the growth of the internet and the ability of the internet backbone to maintain larger routing tables, the need for simple configuration, the requirement for security at the IP level, the need for better support for real time delivery of data (Quality of Service) and increased mobility.
To address these concerns a suite of protocols and standards known as IPv6 has been developed. IPv6 has been designed to be an evolutionary step from IPv4 and natural increments.
All of IPv4's routing algorithms can be used to route IPv6, the only difference being that the addresses in IPv6 are 128 bit long, whereas those in IPv4 are 32 bits in length. New routing capabilities in IPv6 include provider selection, host mobility and auto-readdressing.
With IPv6 neighbor discovery IPv6 solves problems that are related to the interaction between nodes that are attached to the same links. These include, amongst others, router discovery, address resolution, next-stop determination, and neighbor unreachability detection, redirect and neighbor advertisement.
Routing is based on the subnet prefix and the packet's destination IP address. Therefore, packets that are destined for a Mobile Node do not reach the Mobile Node when the Mobile node is not attached to its home link. The home link is the link where the Mobile Node's home IPv6 subnets prefix exists. Regardless of a Mobile Node's movement, a Mobile Node can change its IP address each time it moves to a new link in order to continue communication. However, the Mobile Node does not maintain transport and higher layer connections when it changes location. Hence, IPv6 mobility support is particularly important when recognizing that mobile computers and phones with computing capabilities become a significant population of the Internet in the future.
IPv6 enables a Mobile Node to move from one link to another without changing the Mobile Node's IP address. IPv6 mobility assigns an IP address to the Mobile Node within its home subnet prefix on its home link. This address is known as the node's Home Address (HoA). Therefore, packets that are routed to the Mobile Node's Home Address reach their destination regardless of the Mobile Node's current point of attachment to the Internet, and the Mobile Node can continue communication with other nodes after moving to a new link.
In principle, the same basic components exist in Mobile IPv6 as in Mobile IPv4 except that there are no foreign agents in Mobile IPv6. When a Mobile Node is at home, packets addressed to its Home Address are routed to the Mobile Node's home link using conventional internet routing mechanisms. When a Mobile Node moves to a foreign link the Mobile Node will receive a Care of Address (CoA) and will then send a Binding Update to the Home Address with the Mobile Node's new Care of Address for use while roaming.
After the Mobile Node registers its Care of Address the Home Agent performs proxy neighbor discovery, which means that the home agent multicasts neighbor advertisement on behalf of the Mobile Node. Packets are then sent for the Mobile Node with IPv6 encapsulation.
The following description is based on the standard language used in IP. The link layer normally includes the device driver in the operating system and the corresponding network interface card and the computer. Together they handle all the hardware details of physically interfacing with the cable or whatever type of media is being used. The network layer handles the movement of packets around the network. For example the routing of packets takes place here. The link layer is the lowest layer in the Internet protocol suite.
With Mobile IPv6 a Mobile Node (MN) is reachable by its Home Address even when away from home. For this the MN is associated with a Care-of Address (CoA), which provides information about the Mobile Node's current location. The Home Agent (HA) of the MN and also a Correspondent Node (CN) set up a binding between the Home Address and the Care-of Address in a cache and packets destined for the Mobile Node are directly sent to the Care-of Address. If the MN is at its home network, it deregisters the Care-of Address and receives packets directly with its Home Address.
In order to allow a HA to intercept traffic for a node the proxy Neighbor Advertisements of the Neighbor Discovery protocol are used. According to Mobile IPv6 if there is a Binding Cache entry in the HA for a MN, the HA sends proxy Neighbor Advertisements so that the Neighbor Cache entries of the Nodes in the vicinity of the HA are updated and all traffic to the MN is sent to the link-layer address of the HA.
In the IETF discussions are ongoing how to enhance Mobile IPv6 to support Mobile Nodes with multiple interfaces This simultaneous use of the multiple interfaces increases service quality for the terminals and makes better use of the network capacity.
It is proposed to allow multiple bindings (i.e. multiple Care-of Addresses per Home Address) with filter mechanisms in the HAs to tunnel on per-flow basis to different CoAs (see FIG. 1). For this the Binding Update can for example contain the flow label of the IPv6 header as filter. Further a new bit is introduced in the Binding Update informing HAs about multiple simultaneous bindings. In FIG. 1 an MN connected to two foreign networks is shown. The MN has registered the two CoAs and filter parameters with the Home Agent and receives one flow over foreign network 1 and another flow over foreign network 2.
The scenario addressed by this invention is based on the following general assumptions:
The MN has at least one Home Address (HoA) and multiple interfaces
The MN wants to use the same Home Address with multiple interfaces simultaneously for different flows
The MN wants to use the multiple interfaces also when one interface is connected to the home network
There may be several routers connected to the home link, i.e. Home Agent is not the only router on the home link
When returning home, i.e. one of the MN's interfaces is attached to the home link, two possible approaches are described in the state of the art.
In the first approach the MN sends a BU to the HA with its Home Address as CoA and the home registration bit set and lifetime set to zero, to instruct its Home Agent to no longer intercept or tunnel packets for it. In this case the Home Agent deletes all the bindings from the Binding Cache and stops sending proxy Neighbor Advertisements. On the other hand the MN starts to send Neighbor Advertisements on the home link, so that the Neighbor Cache entries in the Routers are changed and all traffic is directly sent to the MN.
In the second approach the MN de-registers the binding for the interface on the home link and stops using the interface. In this case all traffic previously sent to the de-registered interface is then sent to the remaining registered interfaces according to the filter rules.
In both scenarios it is not possible for the MN to use the home link and a foreign link simultaneously.
The simple solution for the identified problem would be for the MN to acquire a Care-of Address even on its home link and not using the Home Address directly. Then instead of sending a BU with the HoA as CoA, the MN registers the CoA with the HA and sets the multiple bindings bit in the BU.
In addition it is required, that the MN deactivates the Home Address on the interface connected to the home link.
Major drawback of this solution is, that packets between HA and MN are IP encapsulated, this results in higher packet overhead, although the MN is connected to its home link and can receive packets directly sent to its HoA.